840638217 has 4 divisors (see below), whose sum is σ = 1120850960. Its totient is φ = 560425476.

The previous prime is 840638207. The next prime is 840638231. The reversal of 840638217 is 712836048.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 840638217 - 2⁶ = 840638153 is a prime.

It is a super-2 number, since 2×840638217² = 1413345223761878178, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (840638207) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 140106367 + ... + 140106372.

It is an arithmetic number, because the mean of its divisors is an integer number (280212740).

Almost surely, 2^840638217 is an apocalyptic number.

It is an amenable number.

840638217 is a deficient number, since it is larger than the sum of its proper divisors (280212743).

840638217 is a wasteful number, since it uses less digits than its factorization.

840638217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280212742.

The product of its (nonzero) digits is 64512, while the sum is 39.

The square root of 840638217 is about 28993.7616910949. The cubic root of 840638217 is about 943.7776968788. Note that the first 3 decimals are identical.

The spelling of 840638217 in words is "eight hundred forty million, six hundred thirty-eight thousand, two hundred seventeen".